To get standing room a dropped floor is sometimes used. A fixed rigid box dropped area is more common. A less common way is with sliding parts or a fabric part so the floor can be lowered when parked, maybe all the way to the ground. A pod that sits on a trailer that has a solid floor can't do that.
When you store the pod without the trailer on blocks in the back yard it takes less space than a trailer by the amount that the A frame and coupler stick out.
A floor that has a section that drops to the ground could allow the roof height to be lowered a foot. Parked in the yard a foot shorter would look smaller.